Maximum Power Point Tracking (MPPT) is an electronic system that enables photovoltaic (PV) modules to deliver the maximum available power. MPPT is frequently used by PV power conversion system in conjunction with mechanical tracking that physically moves the modules. For example, a perturb and observe (P&O) MPPT method is described by N. Femia, et al., “A Technique for Improving. P&O MPPT Performances of Double-Stage Grid-Connected Photovoltaic Systems,” IEEE Trans. Ind. Electron., vol. 56, no. 11, pp. 4473-4482. November 2009. The incremental conductance (INC) MPPT is described by F. Liu, et al., “A Variable Step Size INC MPPT Method for PV Systems,” IEEE Trans. Ind. Electron., vol. 55, no. 7, pp. 2622-2628, July 2008. A fractional open-circuit voltage based MPPT is described by M. Masoum, et. al., “Theoretical and experimental analyses of photovoltaic systems with voltage and current-based maximum power-point tracking,” IEEE Trans. Power Convers., vol. 17, no. 4, pp. 514-522, Dee, 2002. A fractional short-circuit current based MPPT is described by T. Noguchi et al., “Short-current pulse-based maximum-power-point tracking method for multiple photovoltaic and converter module system,” IEEE Trans. Ind. Electron., vol. 49, no. 1, pp. 217-223, February 2002.
However, those MPPT methods are not reliable for applications with multiple local maximum power points. When the photovoltaic modules in the photovoltaic array perform differently, multiple local maximum power points of the power outputted by the photovoltaic array may occur. Considerable power loss can be incurred when a local maximum power point is tracked instead of the global maxi mum power point.
Accordingly, there is a need for MPPT method, which is suitable for real-time global maximum power point tracking under multiple local maximum power points conditions, for photovoltaic arrays.